Vattel derives a system of law governing the nation-state and relations between nations, from his natural law hypothesis. To have legitimacy, all law written by man must be coherent with this natural law hypothesis. Throughout his work, Vattel constantly addresses the leaders of nations, that a well functioning state will only exist, if they govern so that every citizen is encouraged to develop within himself those agapic qualities needed for society to flourish.

Prefaces – There are many issues and editions, this link will lead you to research areas;